Polyimidazolium protects against an invasive clinical isolate of Salmonella Typhimurium
Frequent outbreaks of Salmonella Typhimurium infection in both the animal and human population with potential for zoonotic transmission pose a significant threat to the public health sector. The rapid emergence and spread of more invasive multidrug-resistant clinical isolates of Salmonella further highlight the need for the development of new drugs with effective broad-spectrum bactericidal activities. Synthesis and evaluation of main-chain cationic polyimidazolium 1 (PIM1) against several gram-positive and gram-negative bacteria have previously demonstrated the efficacy profile of PIM1. The present study focuses on antibacterial and anti-biofilm activities of PIM1 against Salmonella both in vitro and in ovo setting. In vitro, PIM1 exhibited bactericidal activity against all tested three strains of Salmonella at a low dosage of 8 g/ml. Anti-biofilm activity of PIM1 was evident with complete inhibition for the initial attachment of biofilms at 16 g/ml and degradation of pre-formed biofilms in a dose-dependent manner. During the host cell infection process, PIM1 reduces extracellular bacterial adhesion and invasion rates to limit the establishment of infection. Once intracellular, the drug-resistant strain was tolerant and protected from PIM1 treatment. In a chicken egg infection model, PIM1 exhibited therapeutic activity for both Salmonella strains with stationary-phase and exponential-phase inocula. Moreover, PIM1 showed a remarkable efficacy against the stationary phase inocula of drug-resistant Salmonella by eliminating the bacteria burden in >50% of infected chicken egg embryos. Collectively, PIM1 has demonstrated its potential as a drug candidate for treatment of Salmonella infections, as well as a solution to tackle egg contamination issues on poultry farms.